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The present invention provides devices for the endoluminal placement of prostheses, particularly within the vascular system for the treatment of peripheral and cardiovascular disease, such as vascular stenoses, dissections, aneurysms, and the like. The apparatus, however, are also useful for placement in other body lumens, such as the ureter, urethra, biliary tract, gastrointestinal tract, trachea and the like, for the treatment of other conditions which may benefit from the introduction of a reinforcing or protective structure within the body lumen. The prostheses will be placed endoluminally. As used herein, xe2x80x9cendoluminallyxe2x80x9d will mean placement by percutaneous or cutdown procedures, wherein the prosthesis is translumenally advanced through the body lumen from a remote location to a target site in the lumen. In vascular procedures, the prostheses will typically be introduced xe2x80x9cendovascularlyxe2x80x9d using a catheter over a guidewire under fluoroscopic guidance. For vascular applications the catheters and guidewires may be introduced through conventional access sites to the vascular system, such as through the femoral artery, or brachial and subclavian arteries, for access to the target site.
An endoluminal prosthesis typically comprises at least one radially expansible, usually cylindrical, body segment. By xe2x80x9cradially expansible,xe2x80x9d it is meant that the body segment can be converted from a small diameter configuration (used for endoluminal placement) to a radially expanded, usually cylindrical, configuration which is achieved when the prosthesis is implanted at the desired target site. The prosthesis may be non-resilient, e.g., malleable, thus requiring the application of an internal force to expand it at the target site. Typically, the expansive force can be provided by a balloon catheter, such as an angioplasty balloon for vascular procedures. Alternatively, the prosthesis can be self-expanding. Such self-expanding structures are provided by a temperature-sensitive superelastic material, such as Nitinol, which naturally assumes a radially expanded condition once an appropriate temperature has been reached. The appropriate temperature can be, for example, a temperature slightly below normal body temperature; if the appropriate temperature is above normal body temperature, some method of heating the structure must be used. Another type of self-expanding structure uses resilient material, such as a stainless steel or superelastic alloy, and forming the body segment so that it possesses its desired, radially-expanded diameter when it is unconstrained, e.g., released from radially constraining forces a sheath. To remain anchored in the body lumen, the prosthesis will remain partially constrained by the lumen. The self-expanding prosthesis can be delivered in its radially constrained configuration, e.g. by placing the prosthesis within a delivery sheath or tube and retracting the sheath at the target site. Such general aspects of construction and delivery modalities are well-known in the art and do not comprise part of the present invention.
The dimensions of a typical endoluminal prosthesis will depend on its intended use. Typically, the prosthesis will have a length in the range from 0.25 cm to 10 cm, usually being from about 0.8 cm to 5 cm, for vascular applications. The small (radially collapsed) diameter of cylindrical prostheses will usually be in the range from about 1 mm to 10 mm, more usually being in the range from 1.5 mm to 6 mm for vascular applications. The expanded diameter will usually be in the range from about 2 mm to 30 mm, preferably being in the range from about 3 mm to 15 mm for vascular applications.
One type of endoluminal prosthesis includes both a stent component and a graft component. These endoluminal prostheses are often called stent grafts. A stent graft is typically introduced using a catheter with both the stent and graft in contracted, reduced-diameter states. Once at the target site, the stent and graft are expanded. After expansion, the catheter is withdrawn from the vessel leaving the stent graft at the target site.
Grafts are used within the body for various reasons, such as to repair damaged or diseased portions of blood vessels such as may be caused by injury, disease, or an aneurysm. It has been found effective to introduce pores into the walls of the graft to provide ingrowth of tissue onto the walls of the graft. With larger diameter grafts, woven graft material is often used. In small diameter vessels, porous fluoropolymers, such as PTFE, have been found useful.
Coil-type stents can be wound about the catheter shaft in torqued compression for deployment. The coil-type stent can be maintained in this torqued compression condition by securing the ends of the coil-type stent in position on a catheter shaft. The ends are released by, for example, pulling on wires once at the target site. See, for example, U.S. Pat. Nos. 5,372,600 and 5,476,505. Alternatively, the endoluminal prosthesis can be maintained in its reduced-diameter condition by a sleeve; the sleeve can be selectively retracted to release the prosthesis. A third approach is the most common. A balloon is used to expand the prosthesis at the target site. The stent is typically extended past its elastic limit so that it remains in its expanded state after the balloon is deflated and removed. One balloon expandable stent is the Palmaz-Schatz stent available from the Cordis Division of Johnson and Johnson. Stents are also available from Medtronic of Santa Rosa, Calif. and Guidant Corporation of Indianapolis, Ind.
The present invention is directed to a placement catheter assembly which facilitates placement of an endoluminal prosthesis by reducing the maximum size of the endoluminal prosthesis during placement. The present invention finds particular utility for the percutaneous insertion of an endoluminal prosthesis.
The placement catheter assembly, according to one embodiment, comprises a hollow outer shaft and an inner shaft movably housed within the outer shaft. A radially-expansible endoluminal prosthesis is mounted about the inner shaft between the distal ends of the inner and outer shafts. A distal end attachment device comprises a distal end release element, such as a pull wire, which is carried by the inner shaft and releasably secures the prosthesis to the inner shaft. A proximal end attachment device comprises a proximal end release element, also typically a pull wire, which is carried by the outer shaft and releasably secures the prosthesis to the outer shaft. The prosthesis in the radially contracted state and the distal and proximal end release elements together have a maximum diameter which is at most about equal to the diameter of the distal part of the outer shaft to facilitate placement of the prosthesis.
Several advantages may be realized by various embodiments of the present invention. In particular, the invention may permit the user to access smaller vessels and may require smaller access sites resulting in shorter incisions, less pain for the patient and quicker healing. The use of smaller diameters may help to reduce or eliminate disruption to plaque at a target site. Limiting the diameter of the device may help to, in general, reduce complications arising from the procedure.
Other features and advantages of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.